From: peterz@infradead.org (Peter Zijlstra)
To: linux-arm-kernel@lists.infradead.org
Subject: [BUG] 2.6.37-rc3 massive interactivity regression on ARM
Date: Thu, 09 Dec 2010 18:55:30 +0100 [thread overview]
Message-ID: <1291917330.6803.7.camel@twins> (raw)
In-Reply-To: <AANLkTikd3X4pLs5De-LO6=XD+JqUz3-Ku7YM8+0-oK8t@mail.gmail.com>
On Thu, 2010-12-09 at 09:43 -0800, Venkatesh Pallipadi wrote:
>
> The same problem will be there with below code, with irq_delta >
> delta, clock_task can go backwards which is not good.
> + delta -= irq_delta;
> + rq->clock_task += delta;
>
> The reason for this is rq->clock and irqtime updates kind of happen
> independently and specifically, if a rq->clock update happens while we
> are in a softirq, we may have this case of going backwards on the next
> update.
But how can irq_delta > delta?, we measure it using the same clock.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Venkatesh Pallipadi <venki@google.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
Mikael Pettersson <mikpe@it.uu.se>, Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
John Stultz <johnstul@us.ibm.com>
Subject: Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM
Date: Thu, 09 Dec 2010 18:55:30 +0100 [thread overview]
Message-ID: <1291917330.6803.7.camel@twins> (raw)
In-Reply-To: <AANLkTikd3X4pLs5De-LO6=XD+JqUz3-Ku7YM8+0-oK8t@mail.gmail.com>
On Thu, 2010-12-09 at 09:43 -0800, Venkatesh Pallipadi wrote:
>
> The same problem will be there with below code, with irq_delta >
> delta, clock_task can go backwards which is not good.
> + delta -= irq_delta;
> + rq->clock_task += delta;
>
> The reason for this is rq->clock and irqtime updates kind of happen
> independently and specifically, if a rq->clock update happens while we
> are in a softirq, we may have this case of going backwards on the next
> update.
But how can irq_delta > delta?, we measure it using the same clock.
next prev parent reply other threads:[~2010-12-09 17:55 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-27 15:16 [BUG] 2.6.37-rc3 massive interactivity regression on ARM Mikael Pettersson
2010-11-27 15:16 ` Mikael Pettersson
2010-12-05 12:32 ` Mikael Pettersson
2010-12-05 12:32 ` Mikael Pettersson
2010-12-05 13:17 ` Russell King - ARM Linux
2010-12-05 13:17 ` Russell King - ARM Linux
2010-12-05 14:19 ` Russell King - ARM Linux
2010-12-05 14:19 ` Russell King - ARM Linux
2010-12-05 16:07 ` Mikael Pettersson
2010-12-05 16:07 ` Mikael Pettersson
2010-12-05 16:21 ` Russell King - ARM Linux
2010-12-05 16:21 ` Russell King - ARM Linux
2010-12-08 12:40 ` Peter Zijlstra
2010-12-08 12:40 ` Peter Zijlstra
2010-12-08 12:55 ` Russell King - ARM Linux
2010-12-08 12:55 ` Russell King - ARM Linux
2010-12-08 14:04 ` Peter Zijlstra
2010-12-08 14:04 ` Peter Zijlstra
2010-12-08 14:28 ` Russell King - ARM Linux
2010-12-08 14:28 ` Russell King - ARM Linux
2010-12-08 14:44 ` Peter Zijlstra
2010-12-08 14:44 ` Peter Zijlstra
2010-12-08 15:05 ` Russell King - ARM Linux
2010-12-08 15:05 ` Russell King - ARM Linux
2010-12-08 15:43 ` Linus Walleij
2010-12-08 15:43 ` Linus Walleij
2010-12-08 20:42 ` john stultz
2010-12-08 20:42 ` john stultz
2010-12-08 23:31 ` Venkatesh Pallipadi
2010-12-08 23:31 ` Venkatesh Pallipadi
2010-12-09 12:52 ` Peter Zijlstra
2010-12-09 12:52 ` Peter Zijlstra
2010-12-09 17:43 ` Venkatesh Pallipadi
2010-12-09 17:43 ` Venkatesh Pallipadi
2010-12-09 17:55 ` Peter Zijlstra [this message]
2010-12-09 17:55 ` Peter Zijlstra
2010-12-09 18:11 ` Venkatesh Pallipadi
2010-12-09 18:11 ` Venkatesh Pallipadi
2010-12-09 18:55 ` Peter Zijlstra
2010-12-09 18:55 ` Peter Zijlstra
2010-12-09 22:21 ` Venkatesh Pallipadi
2010-12-09 22:21 ` Venkatesh Pallipadi
2010-12-09 23:16 ` Peter Zijlstra
2010-12-09 23:16 ` Peter Zijlstra
2010-12-09 23:35 ` Venkatesh Pallipadi
2010-12-09 23:35 ` Venkatesh Pallipadi
2010-12-10 10:08 ` Peter Zijlstra
2010-12-10 10:08 ` Peter Zijlstra
2010-12-10 13:17 ` Peter Zijlstra
2010-12-10 13:17 ` Peter Zijlstra
2010-12-10 13:27 ` Peter Zijlstra
2010-12-10 13:27 ` Peter Zijlstra
2010-12-10 13:47 ` Peter Zijlstra
2010-12-10 13:47 ` Peter Zijlstra
2010-12-10 16:50 ` Russell King - ARM Linux
2010-12-10 16:50 ` Russell King - ARM Linux
2010-12-10 16:54 ` Peter Zijlstra
2010-12-10 16:54 ` Peter Zijlstra
2010-12-10 17:18 ` Eric Dumazet
2010-12-10 17:18 ` Eric Dumazet
2010-12-10 17:49 ` Peter Zijlstra
2010-12-10 17:49 ` Peter Zijlstra
2010-12-10 18:14 ` Eric Dumazet
2010-12-10 18:14 ` Eric Dumazet
2010-12-10 18:39 ` Christoph Lameter
2010-12-10 18:39 ` Christoph Lameter
2010-12-10 18:46 ` Peter Zijlstra
2010-12-10 18:46 ` Peter Zijlstra
2010-12-10 19:51 ` Christoph Lameter
2010-12-10 19:51 ` Christoph Lameter
2010-12-10 20:07 ` Peter Zijlstra
2010-12-10 20:07 ` Peter Zijlstra
2010-12-10 20:23 ` Christoph Lameter
2010-12-10 20:23 ` Christoph Lameter
2010-12-10 20:32 ` Peter Zijlstra
2010-12-10 20:32 ` Peter Zijlstra
2010-12-10 20:39 ` Eric Dumazet
2010-12-10 20:39 ` Eric Dumazet
2010-12-10 20:49 ` Eric Dumazet
2010-12-10 20:49 ` Eric Dumazet
2010-12-10 21:09 ` Christoph Lameter
2010-12-10 21:09 ` Christoph Lameter
2010-12-10 21:22 ` Eric Dumazet
2010-12-10 21:22 ` Eric Dumazet
2010-12-10 21:45 ` Christoph Lameter
2010-12-10 21:45 ` Christoph Lameter
2010-12-10 17:56 ` Russell King - ARM Linux
2010-12-10 17:56 ` Russell King - ARM Linux
2010-12-10 18:10 ` Peter Zijlstra
2010-12-10 18:10 ` Peter Zijlstra
2010-12-10 18:43 ` Peter Zijlstra
2010-12-10 18:43 ` Peter Zijlstra
2010-12-10 19:17 ` Russell King - ARM Linux
2010-12-10 19:17 ` Russell King - ARM Linux
2010-12-10 19:37 ` Peter Zijlstra
2010-12-10 19:37 ` Peter Zijlstra
2010-12-10 19:25 ` Peter Zijlstra
2010-12-10 19:25 ` Peter Zijlstra
2010-12-13 14:33 ` Jack Daniel
2010-12-13 14:33 ` Jack Daniel
2010-12-06 21:29 ` Venkatesh Pallipadi
2010-12-06 21:29 ` Venkatesh Pallipadi
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